ESR1 and breast cancer: Early studies reported that the HR+/HER2+ subtype was associated with better prognoses of breast cancer patients than the hormone-receptor-negative (HR–)/HER2+ subtype.[34,35] On the contrary, Bae et al[36] found no difference in OS of her2+ breast cancer patients in the comparison among four subtypes (estrogen receptor-positive [ER+]/[PR+], ER–/PR+, ER+/progesterone receptor-negative [PR–], ER–/PR–).